The present invention relates generally to a hydraulic shock absorber for an automotive vehicle suspension. More specifically, the invention relates to a shock absorber having a vortex chamber in a piston, in which the dimensions of the piston are such that it maximizes the absorbing force created by the vortex therein in response to the substantially unstable vehicle driving conditions and minimize the absorbing force in stable driving conditions.
Conventionally, it has been well known to use a shock absorber having a vortex valve in the piston thereof. Generally, in a shock absorber with a vortex valve, the vortex in the vortex chamber in the piston is generated corresponding to the flow amount of the working fluid. The vortex generated in the vortex chamber limits the fluid flow between the upper and lower fluid chambers defined in the absorber housing and separated by the piston.
Since such a vortex valve shock absorber produces the absorbing force against the shock mainly depending on the piston stroke and not depending substantially on the motion speed of the piston, the absorbing force can be reduced in a range where the piston stroke is relatively small and therefore a significant absorbing force is not required. This ensures a comfortable ride.
However, in spite of the above-mentioned advantages which are expected from such a vortex valve shock absorber, a shock absorber which is capable of sufficiently varying the absorbing force substantially corresponding to the requirement according to the vehicle driving condition has not been achieved.